Tag Archives: disassembly

Today’s report contains special instructions for the disassembly of a Feinwerkbau 150 air rifle — for those few places where it departs from the FWB 300 instructions presented in Parts 1 and 2. It was translated and written for us by reader CptKlotz.

This article was originally published on the German co2air forums (www.co2air.de). It was created by the users Pellet (original text guide), Paramags (additional information and FWB150 details ) and boerni (photos and forum post). They kindly gave me permission to translate their guide so people who can’t read German can use it as well. The original forum post can be found here.

Today’s report is a translation that describes how to disassemble a Feinwerkbau 300 air rifle. It was written for us by reader Stephan Szlosze, who we know as CptKlotz, our intrepid German airgunner. We are breaking this into 3 parts because of the large number of photos.

Before I turn this over, I want to emphasize that disassembly of an airgun is both dangerous to the person doing the work as well as to the rifle. Do not undertake this project unless you have read and understood all the instructions.

Today, we’ll look at the performance of the Diana 45 that we tuned recently. Although a new mainspring was installed, it has the same power as the spring that was in the rifle, so no vast power increase was anticipated. If there’s any increase at all, it will probably come from the new breech seal I installed. The old one was flat and hard, so the breech is probably sealing air better now.

The point of this tune was to eliminate as much vibration as we could. The rifle’s owner, Johnny Hill, did not like the buzz that came with every shot, and I told him that most or even all of that could be eliminated by tightening the tolerances inside the powerplant. At my request, he made a larger spring guide, and he buttoned the piston to take out as much vibration as possible.

Barrel must go on
I’ll pick up where I left off in the last report. To assemble the parts, the barrel has to go on the spring tube. During disassembly, I’d noticed during that the breech seal was flattened and hard, so it was replaced before anything else was done. It’s just an o-ring with a steel spacer underneath, so the old one was pried out and a new one was pressed into the groove.

Today, I’ll show you all the things that have been done to the Diana 45 parts; and I’ll clean, lubricate and assemble the rifle. This will be a long report, so I am breaking it into two parts — today and tomorrow.

Piston head swaged
Before we get to the job though, I was asked by one reader to show how the piston head is attached to the piston body. If you want to replace the leather piston seal, the piston head has to be removed — and that isn’t going to be easy, because it is mechanically swaged onto the piston body.

We have a lot to cover today, so let’s get right to it. We left the Diana 45 with the mainspring out of the gun at the end of yesterday’s report. The only thing left in the disassembly is to remove the piston. Do not disassemble a gun if you’re not 100% certain you can put it back together again in safe working condition!

Remove the barrel
The piston will not come out of the gun until the cocking link that connects it to the underside of the barrel (for cocking) is removed. To do that, you must first separate the barrel from the spring tube. That step is easy on some breakbarrels, but not so easy with this 45. On most breakbarrels, you remove the pivot bolt from the action forks and the barrel separates from the spring tube. The Diana 45 has another step; and unless you follow it, the barrel will never come off the gun.

I’m changing things for this report just a bit. In part 3, I told you that I would do a 25-yard accuracy test next. I’ve decided to forego that step and start working on the tuneup, instead. Today, I’ll show how to disassemble a Diana 45. Make certain the rifle is uncocked before you begin. Do not disassemble a gun if you’re not 100% certain you can put it back together again in safe working condition!